In biology, a clasper is a male anatomical structure found some groups of animals, used in mating.

Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve as intromittent organs used to channel semen into the female's cloaca during mating. The act of mating in some fish including sharks usually includes one of the claspers raised to allow water into the siphon through a specific orifice. The clasper is then inserted into the vagina, where it opens like an umbrella to anchor its position. The siphon then begins to contract expelling water and sperm. Male chimaeras have cephalic claspers (tenacula) on their heads, which are thought to aid in holding the female during mating.

In entomology, it is a structure in male insects that is used to hold the female during copulation.

Harry Clasper (5 July 1812 – 12 July 1870) was a Tyneside professional rower and boat builder. He was an innovative boat designer who pioneered the development of the racing shell and the use of outriggers. He is said to have invented spoon-shaped oars.^{[citation needed]}

He was the first of three well-known Tyneside oarsmen, the other two being Robert Chambers and James Renforth.

Harry Clasper was born in Dunston, now part of the Metropolitan Borough of Gateshead, but then an independent village on the south bank of the River Tyne, a mile upriver from Gateshead. Later his family moved to Jarrow, also on the south bank on the Tyne, downriver from Newcastle. At the age of 15, he began to work at Jarrow Pit, which was notorious for firedamp. After a while Clasper decided that mining did not suit him and he became apprenticed as a ship’s carpenter in Brown’s Boatyard, Jarrow. There he learnt about woodworking and the principles of boatbuilding. This would be useful to him in later life.

After a while his family moved back to Dunston and Clasper became employed as a coke burner and wherryman for the Garesfield Coke Company at nearby Derwenthaugh. His work as a wherryman would also serve him well in later life. Clasper then worked for a while at Hawks, Crawshay and Sons Ironworks around the mid 1830s.